BRAIN EVOLUTION EXPLAINED
two studies on brain development & evolution caught the media's attention with flashy data & flashy claims about the relationships between humans, chimps & gorillas. if i understood, these are important pieces in a much bigger puzzle
original articles: Benito-Kwiecinski et al., 2021 (Cell), Ponce de León et al., 2021 (Science), reported in: The Guardian by Ian Sample on 24th March 2021 & The Daily Mail by Stacy Liberatore on 25th March 2021 & The Daily Mail by Johnathan Chadwick on 8th April 2021 & Science News by Charles Choi on 8th April 2021 & The Scientist by Abby Olena on 19th April 2021
this story was in episode 8 #evolvution #parietal #occipital #frontal
the error bar says
two high-profile studies on human brain development & evolution have made the headlines
first, the Guardian & Daily Mail report a study of the development of human, gorilla & chimpanzee brain cells. human cells were artificially manipulated into growing more like gorilla cells, while their number, shape & biological properties were measured. these changes were related to the brain size differences between humans & the other great apes. both newspapers claimed that the puzzle of human brain size is solved
second, Science News, The Scientist & the Mail report a study of ape-like creatures living 1.7 million years ago. 5 skulls were scanned & compared with 33 more recent skulls. the oldest were shown to be more ape-like than human-like. in particular, the researchers focused on changes in the inferior frontal lobe of the brain - one of many important parts of the brain involved in language
have we explained brain development & evolution?
these papers are beyond my expertise, so here is a superficial evaluation
in the first, the media stories are about why 'the human brain' is much bigger than chimps or gorillas. but the brain cells studied were only a few weeks old. we don't know what would happen over months of development, or whether the manipulated human cells would develop like gorillas'
the researchers claimed that their results show that we now understand the evolutionary basis of brain expansion. that's clearly not true. these do look like remarkable results, but more humility would be welcome - even in Science Magazine
the second paper's data are also powerful, beautiful & undoubtedly important contributions to understanding brain evolution
a minor gripe is that the paper could be written more clearly for non-specialist readers. why say "petalial asymmetry cannot be ascertained" when the authors mean: "we don't know if the brain was symmetrical"; why "gnathic morphology" when "jaw shape" is clearer?
the second gripe is bigger. the paper & media coverage focus on the frontal lobe & its possible role in language, tool use & complex thought. these are brain functions that are assumed - often incorrectly - to be specific to humans
but the gorilla in the room of this paper is the massive territory of human brain - probably 3 or 4 times as much - that has also expanded during evolution. why do these parts of the brain - the so-called temporal, parietal & occipital lobes - not get nearly as much attention as the sexy inferior frontal lobe?
this may be a new form of the brain disorder called parietal neglect